So yes, it is truth, not opinion. Sync is a double-edged sword: on one hand, it makes many more people come in, on the other, the general ethos of the Fediverse leans towards FOSS and Sync is not FOSS.
I don't think that's a bad thing. The Lemmy and the wider Fediverse are open and using a closed source client to access that doesn't change anything. Unlike with other closed ecosystems using a closed source client doesn't impact anyone else.
This is genuinely a tough position to address, as I see both parties' sides. I can't blame a dev for setting up a system to ensure he gets paid, I'm on antiwork with a lot of you, raging out about how minimum wage hasn't gone up and employers want to squeeze every last drop of labor out of their employees and give them as little possible in compensation... and I also see the side of wanting the spirit of greed (the source of Reddit's choices that caused the exodus) to not have soil to take root here...
In Sync's defense, it's so far ahead of any of the FOSS apps I tried while I waited for it to release that I don't think it's greedy for the dev to set up a system to earn some compensation for their efforts and whatever ability enabled him to create an app so far ahead of the other Lemmy apps. I wonder how much these other poor devs have made from their work on the other Lemmy apps that have sprouted... might explain why they're lacking in comparison, they can't put as much effort into their app while holding a full time job because unless there's an incentive to compensate, the comments in response to Sync's release have made it apparent that a lot of the lemmy preachers of FOSS are really just cheapskates, whose attraction to the "ethos" is the free stuff, not the principle.
On the other hand, I can understand the price point and the subscription system aren't exactly what many expected or view as "reasonable." For me, $1.99 a month doesn't bother me, I make enough to cover that from Google Opinion Rewards so it's no money out of my pocket. If that amount is too much, go to Network Settings and add "DNS.adguard.com" to your private DNS provider hostname field and don't pay for it. I still don't think it's worth not using the app because you think the dev is greedy for not wanting to work for free. That mentality keeps up, the spez's will start taking notes from us on how to get folks to provide services with no compensation at all!